Conventionally, there are cases where, as a wiper motor for an automobile, a 3-brush-type electric motor is used that is capable of switching speeds of rotation. An electric motor of this type is one in which a plurality of magnets are arranged so as to be spaced in the circumferential direction on an inner circumferential surface of a bottomed-cylinder-like yoke and in which an armature is rotatably arranged on an inner side of these magnets.
The armature includes: an armature core that is fitted onto and fixed to a rotation shaft; an armature coils that are wound around the armature core; and a commutator that is fitted onto and fixed to the rotation shaft so as to be adjacent to the armature core.
A commutator is one in which a plurality of segments are disposed in the circumferential direction in a state of being insulated from each other and in which an end portion of each armature coil is connected to each segment.
Furthermore, with the segments, a plurality of brushes, which are spaced in the circumferential direction, are in sliding contact. Via these brushes, electric power is fed to the armature coils.
The brushes include a low speed brush, a high speed brush, and a common brush that is used as these brushes, and each brush is held in a brush holder stay via each brush holder. Furthermore, the low speed brush and the common brush are arranged at positions 180 degrees away from each other in electrical angle (mechanical angle×the number of pole pairs), and at the same time, the high speed brush is arranged so as to be a predetermined angle spaced from the low speed brush in the circumferential direction. With selective switching of electric current application between the low speed brush and the high speed brush, the speed of the electric motor is made switchable.
In a holder unit, wiring members such as terminals and jump wires are used in order to secure electric current application to each brush. For electrical connection of these wiring members, caulking or resistance welding is used.